摘要:

AbstractWe describe a series of stages for development of the embryo of the zebrafish,Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis—the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope. The descriptions also fully utilize the optical transparancy of the live embryo, which provides for visibility of even very deep structures when the embryo is examined with the compound microscope and Nomarski interference contrast illumination. Photomicrographs and composite camera lucida line drawings characterize the stages pictorially. Other figures chart the development of distinctive characters used as staging aid signposts. ©1995 Wiley‐Liss,

ISSN:1058-8388    

DOI:10.1002/aja.1002030302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGlutamate is the excitatory transmitter at neuromuscular synapses inDrosophila, and electrophysiological studies indicate that the receptors for glutamate are concentrated in muscle fibers at synaptic sites. Acetylcholine is the excitatory transmitter at vertebrate neuromuscular synapses, and previous studies have shown that accumulation of acetylcholine receptors (AChRs) at synaptic sites is controlled both by transcriptional and post‐translational mechanisms. The transcriptional pathway culminates in selective expression of AChR subunit genes in nuclei near the synaptic site, causing AChR mRNA to accumulate in the synaptic region of the muscle fiber. We used a cDNA encoding a subunit of theDrosophilamuscle glutamate receptor (DGluR‐II) to determine the temporal and spatial expression pattern of the DGluR‐II gene during embryogenesis and in larval muscle. We show that DGluR‐II mRNA is first expressed at stage 12 of embryogenesis and that expression is detected in developing dorsal, lateral, and ventral somatic muscles within the next 2 hr. By stage 16 DGluR‐II mRNA is expressed in all somatic muscles and in pharyngeal muscles. In third instar larvae DGluR‐II mRNA is expressed in all body‐wall muscle fibers. DGluR‐IImRNA, however, is expressed throughout the larval muscle fibers and is not concentrated within muscle fibers at neuromuscular synapses. These results indicate that although the DGluR‐II gene is expressed in somatic muscle cells it is not selectively expressed in nuclei near the synaptic site. ©19

ISSN:1058-8388    

DOI:10.1002/aja.1002030303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring their maturation, lens cells lose all membrane bound organelles, including mitochondira. In chicken embryos this process begins in the central lens fibers beginning around embryonic day 12 (E12). Transforming growth factor β (TGFβ) is a multipotent growth modulator thought to play a role in numerous developmental processes. TGFβ1 has been localized to mitochondria in rat liver cells and muscle cells. In the present study, we examined the expression of TGFβ isoform mRNAs and proteins during chicken embryonic lens development. PCR analysis demonstrated TGFβ2 and TGFβ3 trasncripts in the lens epithelium and fibers throughout pre‐ and post‐hatching development. TGFβ isoforms were detected throughout the lens epithelium and fibers early in development (E6). However by E19, the distribution of TGFβ2 and TGFβ3 transcripts and proteins coincided with regions of the lens that contained mitochondria. In addition, intense TGFβ staining was observed in the basal portions of the equatorial epithelial cells, a region with abundant mitochondria. Transcripts for TGFβ1 and TGFβ4 were not detected in any tissue or time frame examined. Similarly, no immunostaining for TGFβ1 was observed. ©199

ISSN:1058-8388    

DOI:10.1002/aja.1002030304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study, we have isolated newly formed somites from the caudal regions of 8.5 day mouse embryos and transplanted them orthotopically into correspondingly staged hosts at the level of the prospective limb‐forming region. The experimental embryos were then cultured intact for 32‐36 hr. The donor somites used were pre‐labelled with DiI, a fluorescent lipophilic dye, or were obtained from transgenic embryos that carried a 1 kb 5′ regulatory sequence of the desmin gene linked to the gene encodingEscherichia coli β‐galactosidase. The transgene is specifically expressed in skeletal muscles (Li et al. [1993] Development 117:947‐959). The aim of these experiments was to show definitively that the musculature of the mammalian limb is derived from the somites. The results demonstrated that DiI‐labelled cells from the implanted somites were able to invade the proximal region of the fore‐limb bud during the course of development. The use of transgenic somites as grafts confirmed that some of the somitic cells found in the limbs were myogenic cells. To determine whether the displacement of somitic cells is an active or passive process, somatopleure obtained from the prospective limb‐forming regions of day 8.5 day embryos was implanted into 8.5 day hosts. We did not detect the presence of DiI‐labelled somatopleural cells in the fore‐limb after 32‐36 hr of culture. This suggests that somitic cells reached the limb bud via active locaomotion rather than as a result of being passively dragged there, as the limb elongates during development. In addition, we injected latex beads into the somites, as probes, to determine whether extracellular matrix‐driven translocation plays a role in driving the somitic cells to the limb bud. In a majority of the specimens examined, we could not detect the presence of these beads in the limb bud. However, in the trunk of these embryos, the beads were found dispersed throughout the ve

ISSN:1058-8388    

DOI:10.1002/aja.1002030305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe report the characterization ofGsh‐1, a novel murine homeobox gene. Northern blot analysis revealed a transcript of approximately 2 kb in size present at embryonic days 10.5, 11.5, and 12.5 of development. The cDNA sequence encoded a proline rich motif, a polyalanine tract, and a homeodomain with strong homology to those encoded by the clustered Hox genes. TheGsh‐1expression pattern was determined for days E8.5 to E13.5 by whole mount and serial section in situ hybridizations.Gsh‐1transcription was restricted to the central nervous system. Expression is present in the neural tube and hindbrain as two continuous, bilaterally symmetrical stripes within neural epithelial tissue. In the mesencephalon, expression is seen as a band across the most anterior portion. There is also diencephalon expression in the anlagen of the thalamus and the hypothalamus as well as in the optic stalk, optic recess, and the ganglionic eminence. Moreover, through the use of fusion proteins containing theGsh‐1homeodomain, we have determined the consensus DNA ninding site of theGsh‐1homeoprotein to be GCT/CA/CATTAG/A. ©1995 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1002030306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe developmental sequence of the embryonic joint has been well studied morphologically. There are, however, no definitive studies of cell function during joint development. In order to begin to understand the differentiation events that contribute to joint formation, we examined the expression of collagen mRNAs encoding types I, IIA, IIB, and XI. In situ hybridization was performed on chicken embryo hind limb buds and digits from day 7 to day 18 (Hamburger and Hamilton stages 31–44). In the day 7 (stage 31) limb bud, there was a condensation of mesenchyme forming the primitive tarsal and metatarsal bones that showed abundant expression of type IIA procollagen message, but no type IIB or type α1(XI) message. By day 8 (stage 33), co‐expression of types IIA, and type XI procollagen mRNAs was observed in the condensations, with expression of IIB restricted to early chondrocytes with metachromatically staining matrix. At this stage, DNA fragmentation characteristic of apoptosis was observed in cells near the midline of the interzone region between the developing anlagen, and in areas between and around the individual digits of the paddle. The presumptive apoptotic cells were more numerous at day 9 (stage 35), and were not found in the developing joint at subsequent time points, including the initiation of spatial cavitation of the joint. From days 11–18, type IIA procollagen mRNA was expressed in flattened cells at the surface of the anlagen, and in the perichondrium and in the developing joint capsule; type IIB mRNA message was found only in chondrocytes. Type XI mRNA was expressed by all type II‐expressing cells. Alpha 1(I) mRNA was expressed early by cells of th8e interzone and capsule, but as cavitation progressed, the type I expressing cells of the interzone merged with the superficial layer of the articular surface. Thus, at the time of joint cavitation, there was a distinct pattern of expression of procollagen messages at the articular surface, with type I being outermost, followed by morphologically similar cells expressing type IIA, then chondrocytes expressing type IIB. The progenitor cells expressing type IIA message define a new population of cells. These cell populations contribute to the molecular heterogeneity of the articular cartilage, and these same populations likely exist in the developing joints of other species. The transient transcription of type II and type XI collagen genes, characteristic of chondrocytes, by cells in the joint capsule demonstrates that these cells may have chondrogenic potential. ©1995 Wiley

ISSN:1058-8388    

DOI:10.1002/aja.1002030307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo understand the hierarchy of developmental controls underlying axis specification in vertebrate embryos, it is helpful to identify relationships between regulatory molecules and the genes that given axial cells their differentiated phenotypes. This work reports the cloning and expression pattern of one of these differentiation genes, a type II collagen (col2a1) gene from the zebrafishDanio rerio. Along th8e embryonic axis,col2a1is expressed dynamically in three rows that are each a single cell wide: the notochord and the rows of cells immediately dorsal and ventral to it—the floor plate of the central nervous system, and the hypochord. In addition,col2a1is expressed in the pharyngeal arches, the epithelium of the otic capsule, and in the mesenchyme of the neurocranium. Experiments probed the expression pattern ofcol2a1relative to that of known or potential regulators of axis development, includingaxial,sonic hedgehog,twist, andcyclops. The results showed that the spatial and temporal pattern ofcol2a1expression in axial mesoderm follows the expression oftwistcloser than other genes tested. Incyclopsembryos, which lack an intact floor plate,col2a1expression was usually low, but not missing in cells in the ventral spinal cord. Becausecol2a1expression reveals abnormalities in the notochord ofcyclopsb16embryos, and lesscol2a1‐expressing mesenchyme accumulates rostral to the notochord incyclopsembryos, the effects of thecyclopsb16mutation are not confined to the central nervous system. ©1995 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1002030308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have identified a novel FGF receptor, Z‐FGFR4, in zebrafish embryos. Z‐FGFR4 is closely related to both chicken FREK (Marcelle et al. [1994] Development 120:683–694) and thePleurodelescDNA clone Pw‐FGFR4 (also named PFR4). The Z‐FGFR4 cDNA clones contain consensus sequences for two groups of two Ig‐like domains, separated by eight acidic residues referred to as the “acid box”. Z‐FGFR4, therefore, is the first FGFR molecule yet described in vertebrates that contains four Ig domains in its aminoterminal region.Whole‐mount in situ hybridization of staged zebrafish embryos, using probes prepared from a variety of domains of the Z‐FGFR4 cDNA, reveal complex temporal and spatial expression patterns. Expression of Z‐FGFR4 mRNA is first detected in embryos prior to gastrulation and then appears in prechordal plate mesendoderm. At this time, Z‐FGFR mRNA is expressed in the epiblast in two distinct stripes which ultimately contribute to the brain. Eventually Z‐FGFR4 transcripts are observed in forebrain, anterior hindbrain (rhombomeres 1, 3), and caudal hindbrain (rhombomere 7), as well as in the dorsal‐most portion of the rostral spinal cord. Expression in axial mesendoderm appears transiently in notochord and segmental plate mesoderm. Eventually, Z‐FGFR4 mRNA becomes restricted to the posterior somites and is absent in differentiated notochord. These detailed expression studies provide the basis for understanding FGFR function through an analysis, currently in progress, of the developmental consequences of Z‐FGFR4 mis

ISSN:1058-8388    

DOI:10.1002/aja.1002030309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1058-8388    

DOI:10.1002/aja.1002030301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY